All rise: Katie Kunz experiments with various strains of yeast at the Brewing Science Institute in Colorado Springs.
John Johnston

This weekend, over 20,000 beer nuts will invade the Colorado Convention Center for the Great American Beer Festival, raising toasts to the brewing artisans who craft their precious drink. But the tippling throng should be hoisting a glass to the unsung hero that most deserves beer-making recognition: yeast.

Yeast -- a lowly, single-cell fungus -- is the living, breathing wonder that makes beer possible. Paul Gatza, director of the Institute for Brewing Studies, an arm of the Association of Brewers that presents the GABF, recognizes this by reciting an old brewing axium. "Brewers make wort," says Gatza, referencing the unfermented liquid. "Yeast makes beer."

Yeast cells consume the sugars in beer, excreting alcohol and carbon dioxide in the process. Thanks to yeast, grape juice is turned into wine, and wort is converted to alcohol-rich, naturally carbonated beer. Without yeast, life would be a dry, sobering existence.

Katie Kunz knows this better than most folks. Her Colorado Springs company, the Brewing Science Institute, is one of the nation's three major yeast suppliers for the craft-brewing trade. Kunz is the company's founder and lone employee. "I'm a one-woman show," she says. "I work very hard."

Most of that work involves propagating slants of individual yeast strains (stored under refrigeration in her lab) into larger amounts needed for "pitching" yeast. To make those amounts, a few pure yeast cells are added to a sterile blend of malt powder, water, zinc, calcium carbonate and other minerals, and the yeast is then allowed to propagate. Kunz's typical order from a craft brewer, for a seven-barrel batch of beer, involves making about twelve gallons of yeasty slurry that she centrifuges down to a two-quart paste of trillions of living cells. She packs the paste into chilled, insulated packaging and ships it overnight to customers across Colorado. In addition to yeast, Kunz also provides brewers with consulting services, isolating good and bad yeast strains and helping breweries make the most of their stock.

It sounds like a science-class dropout's nightmare job, but Kunz loves it. "Yeast is a lot of fun," she gushes. "I love yeast; I do. It's a neat organism. It smells nice while it's propagating. It's interesting to look at under the microscope: You can see it budding, and it's very hardy. And there's the fact that it makes such an interesting product."

Kunz owes her career to her entrepreneurial spirit, the craft-beer trade and a home-brewing boyfriend. After graduating from the University of Colorado's Colorado Springs campus in 1995 with a degree in biology, she was unable to find a job. So she took a tip from mentor James Mattoon, a yeast-genetics professor at CU who saw opportunity in the growing craft-beer trade and let Kunz use the school's lab (for a modest fee) to start BSI.

In the company's first year, Kunz saw her monthly income go from about $50 to a few hundred, and from there she was off and running. By 1998, she was able to open her own lab. Today she makes a good living doing what she loves -- even if most people don't understand the importance of her work. "The average person, the Bud drinker who doesn't think a lot about it, doesn't know that yeast is used in fermenting beer," Kunz explains.

But Kunz finds her work exciting as well as important. The yeast business offers "a lot of intrigue," she reveals. Much of that intrigue revolves around brewers with covert samples of yeast, snuck out of the world's breweries in bottles of beer or small vials. "I have people who come in and say, 'Here's this sample; here's how I got in on the plane. I want you to isolate it and sell it only to me. I'll call it my proprietary strain.'"

Is that legal? "It's genetic material, an organism created by nature," Kunz says. "Pilfering yeast has gone on forever."

Her firm can also make sure that yeast buyers get what they pay for; she even offers DNA testing. Major brewers spend fortunes maintaining their yeast and protecting its secrecy, Kunz notes.

But craft brewers should pay attention to their yeast in other ways, according to AB president and home-brewing/craft-beer guru Charlie Papazian. "Brewers need to love their yeast," he says. "Yeast is a living organism, and it has all kinds of behavioral traits, like human beings. Alter its living conditions and, like any living creature, it won't do what it's supposed to do."

Louis Pasteur is the man who discovered that. The godfather of yeast science, he was the first to isolate yeast and its unique abilities -- research that makes his milk efforts pale in comparison. Before Pasteur figured things out, fermentation was an unexplained gift from the gods that magically converted starchy concoctions, honey and various juices into a heady cocktail. The person who controlled the ferment-inducing goods was a holy man. In the fifteenth century, Gatza points out, the slurry from batches of Brit beer was called "godisgood" and was protected by English law that made sure the common folk had access to it.

Today yeast is just as crucial. "Yeast is the most important element in beer," Gatza says. "Yeast is more important than the malt, the hops, the water." The craft-brewing renaissance has inspired a yeast renaissance, too, and both fields benefit from greater variety. "Ten years ago, the brewer had access to maybe fifteen or twenty strains of good quality," he adds. "Now brewers can get over a hundred different strains of extremely high-quality yeast."

Kunz's library includes over 200 yeast strains. "It's fun to have all these different yeasts," she says, "though most of them I've never propagated. Nobody's ever asked for them. So it's very exciting when somebody calls up and says, 'You know, I want to try that ABS-3; what is that?' Brewers are an experimental people, and they have as much fun brewing with the yeast as I do propagating yeast."

Without her favorite fungus, "life would be very boring in a lot of ways," she says. "We wouldn't have leavened bread, a mainstay of humankind for thousands of years. We wouldn't have most fermented beverages."

We also wouldn't have the Great American Beer Festival (, which should toast the single-celled magicians that turn yeast into beer, life into a celebration. Hell, if the world had its priorities straight, there'd be a statue of a yeast cell in every nation's capital.

At the very least, there should be another annual beer-minded celebration honoring the world's best brewers: the Great American Yeast Festival. "I think that's a great idea," says Kunz.

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